Disclosed are a scratch color-developable ink comprising an electron-donating colorless or light-color dye precursor, an electron-accepting color developer and a varnish, wherein a solid particle component contained therein has an average particle diameter of 0.3 to 25 μm, a scratch color-developable ink comprising an electron-donating colorless or light-color dye precursor, an electron-accepting color developer and a varnish, wherein an azaphthalide compound is contained as the electron-donating colorless or light-color dye precursor, and an invisible information printed sheet obtained by printing invisible information on a support with the above scratch color-developable ink.The above scratch color-developable ink makes invisible information visible easily by scratching with a finger nail although the color of an invisible information printed portion is hard to develop by frictional contact during usual handling, gives a high developed color intensity and is free from the occurrence of dust during the visualization of invisible information.